sutton



Feb. 7, 1956 R. w. SUTTON 2,733,901

CARBURETOR Filed Sept. 29, 1951 2 Sheets-Sheet 1 INVENTOR.

E0552 W Jurro/v W W. aiw

' ATTORNEY United 3 Claims. c1. 261-41) This invention relates to chargeforming devices for internal combustion engines having a variablythrottled air supply, and more particularly to idle systems for suchengines.

Engine idling. requirements present special problems to be met by aninjection carburetor since the air flow to the engine is so low in theidle range that insufiicient air metering forces are set up in thepressure regulator to accurately establish the required fuel to airratios. Idle valves and various valve adjustments have been used in thepast to satisfy the engine requirements in this range. However, theproblem of insuring smooth engine running at slow idle remains.

It is therefore a principal object of this invention to insure smoothrunning of the engine at slow idlecondi tions.

It isa further object of this invention to provide an idle system whichwill meet wide variations in engine requirements throughout the idlerange.

Another object of this invention is to provide an idle systemv whichoperates independently of manifold suction and. which discharges fuel tothe engine throughout the range of operation of the engine.

Other objects and advantages will be readily apparent from. thefollowing detailed description taken in connection with the accompanyingdrawings in which:

Figure 1: is a schematic sectional view of a carburetor in which oneembodiment of my invention is shown;

Figure 2 is a partial section of. the carburetor shown in Figure 1including another embodiment of my invention;

Figure 3 is a partial section of the carburetor shown in Figure 1 inwhich a third embodiment of my invention is disclosed;

Figure 4 is a partial section of the carburetor shown in Figure l inwhich a manual engine priming control is shown in combination with theslow idle system; and

Figure 5 is a plan view of the mechanism shown in Figure 4'.

Referring first to Figure l, a main body or housing is shown at numeralhaving an air induction passage 12 I therethrough with an air inlet at14 and an air outlet at 116; Main body 10 is adapted to be connected toan air horn or scoop on theair inlet side and to a supercharger inlet orto the intake manifold of an internal combustion engine on the airoutlet side thereof. Housed within said air induction passage is aventuri 18 having an annular passage 20 at the throat thereof subjectedto venturi suction. Downstream of venturi 18 in the induction passagetes Patent 0 ice 2- thereto by valve extension 54 and stem 56. When fuelis flowing, a constant rate compression spring 58- abuts diaphragmassembly 30' at 60 and acts to open the regulator valve in opposition toa" small compression spring 62 and the fuel: pressure in chamber 28.Pressurized fuel is supplied to chamber 28 by a pump (not shown) throughfuel inlet port 64, conduit 66 and valve controlled port 52.

A main metering jet 68 in series with regulator valve portv 52: connectschamber 28 to main fuel passage 70', which passage is connected to acritical flow nozzle 72 by means of an idle valve port 74, a conduit 76,and a-- main discharge valve port. 78. Air is supplied to the nozzlethrough conduits 38, 79 and 81 to minimize the effect of engine suctionon fuel delivery. The discharge nozzle 72 is described and claimed inPatent No. 2,457,765 to Winkler.

The effective area of idle valve port 74 is controlled by axiallymovable idle needle valve 80 which is concentric with and: rigidlyattached to scaling diaphragm 82. A rightward or closing movement isimparted to valve 80 by manual idle control rod 84 when the throttlelever 86- is moved to an idle position. Chamber 88 to the left ofdiaphragm 82 is vented to venturi suction through a conduit 90 so thatthe fuel to air differential pressure across diaphragm 82' will causevalve 80: to follo-wjthe movement of. throttle lever 86 throughout theidle range. v

The basic carburetor shown in Figure 1', including the discharge nozzlevalve asembly shown generally at 92-, is described and claimed in PatentNo. 2,445,846 to Barfo'd et al.,. said valve assembly being composed ofchambers 94 and 96 separated by a diaphragm 98, and said chambers beingvented to venturi suction and metered fuel pressure respectively. Acompression spring 100, which may be adjusted by an adjustingscrew 101,acts on the venturi side of diaphragm 98 and movements of said diaphragmare imparted to valve 102 which controls the effective area of port 78.

An acceleration pump which is shown generally at 104 consists ofchambers 106 and 108 separated by a spring loaded diaphragm 110, chamber106 being vented to manifold suction through conduit 112 and 'charnber'108 being vented. to metered fuel pressure in conduit '70 spring loadeddiaphragm 122' which controls a valve 124 concentric therewith, so as tovary the effective area of a. port 126 after the differential pressureacross said diaphragm reaches a predetermined amount. Chamber 1 18 isvented through conduit 128 to the venturi suction in chamber 26, whilechamber is vented to unmetered fuel pressure in chamber 28 throughconduit 130. At some predetermined unmetered fuel pressure valve 124opens allowing the necessary enrichment to occur while the engine isoperating in the power range.

A manual mixture control valve 132 controls the effective area of acalibrated passage 134 which connects chamber 24 with chamber 26 throughconduits 34, '36 and 40. Valve 132 is remotely controlled by the pilotby means of a linkage (not shown) connected to lever 136. Clockwiserotation of lever 136' moves arm 138 rightwardly to abut cam 140 andmove valve 132" varying amounts out of port 134; This provides means forauto rich or auto-lean operationas desired by the pilot. As

valve 132 is moved to open port 134 auto-lean operation 3 is approachedsince the venturi suction in chamber 26 is progressively bled down,thereby decreasing the unmetered fuel pressure required to balance theair metering force. As valve 132 is moved toward closed position thereverse effect occurs. When the engine is stopped fuel flow thereto iscut off by moving valve 132 to a full rightward position in whichposition cam 140 depresses lever 142 resulting in an upward movement ofidle cutofi plunger 144 against lever 146 to compress spring 58 andallow regulator valve to close.

In parallel with said manual mixture control device is automatic mixturecontrol unit or altitude control 148 covered by Patent No. 2,469,038 toWinkler. Chamber 24 communicates with annulus through conduits 34, 36and 150, chamber 152, a port 154, conduits 156, 42 and 44, restrictionor mixture control bleed 46, and chamber 48, the area of said port 154varying inversely as a function of altitude density. As entering airdensity decreases bellows 157 expands moving contoured mixture controlvalve 157' to further open port 154-.thereby increasing the pressure inchamber 26 as a function of the mass of air flowing to the engine whichin turn causes a decrease in unmetered fuel pressure and a decreasedfuel flow to maintain a constant fuel air ratio for any given powersetting. The reverse operation occurs upon an increase in entering airdensity.

At slow idle valve 102 is nearly closed, resulting in undue sensitivityof said valve to the fuel flowing through port 78. This sensitivity isdue to the velocity of the fuel flowing through said port which tends todraw valve 102 to a fully closed position, resulting in valve vibrationand unsatisfactory engine performance at this minimum flow condition. Toovercome this ditficulty, a separate system is provided which assuresthe proper fuel supply during slow idle. This system includes a fuelpassageway 158, consisting of a conduit 160, chambers 161 and 162,conduit 163, chamber 164 and port 165, for connecting the unmetered fuelchamber 28 with the induction passage 12 on the engine side of throttlevalve 22. A metering jet 166 controlled by a manually adjustable valve168 is disposed between chambers 161 and 162. Chamber 164 in main bodyhousing 10 communicates with impact air pressure through conduit 38 andpassage 79 to minimize the effect of engine suction 'on fuel flowthrough passageway 158.

Assuming the carburetor has not been filled with fuel and the idlecutoff plunger 144 is in the position shown in Figure 1, the spring 58will urge the diaphragms to the right and open valve 50. Fuel underpressure supplied to conduit 66 enters and fills chamber 28 and flowsthrough metering jet 68 to chamber 96 of the discharge nozzle valve,thence through port 78 and critical flow nozzle 72. As the pressure inchamber 28 increases it acts against the diaphragm 32 and tends tocompress spring 58 whereby the valve 50 tends to close. Fuel underpressure supplied to chamber 96 acts on diaphragm 98 and tends to openvalve 102., The adjusting screw 101 is normally adjusted to compressspring 100 to such a point that a slightly lower pressure is required inchamber 96 to open the valve 102 than is required in chamber 28 topermit the valve 50 to close. It is apparent that the actual values ofthe fuel pressures will be determined by the strength of the springs 58and 100, the pressure required being greater as the strength of thesprings is increased.

During operation, assuming the. area ratio of the diaphragms and 32 istwo to one, the regulator unit 23 functions to maintain a differentialfuel pressure across the metering jet 68 and, if the engine is operatingin the high power range, across port 126 which is equal to twice theventuri drop as sensed in chambers 24 and 26. For example, a givendecrease in venturi throat pressure as sensed in chambers 26 and 94, i.e. as compensated by automatic mixture control 148 so that said pressureis proportional to the mass of air flowing, results in an A metered fuelpressure.

4: 1 equal increment increase in the unmetered fuel pressure in chamber28 and in an equal increment decrease in the Consequently the increasein fuel metering differential pressure is equal to twice the increase inair metering differential pressure. Similarly a given increase in airimpact pressure is sensed in chamber 24 and since it acts on a diaphragmhaving twice the area of diaphragm 32, the unmetered fuel pressure inchamber 28 is increased an increment double the increase in impact airpressure.

At slow idle, the required fuel is supplied principally throughpassageway 15% whereby the required fixed fuel to air ratio isestablished. Fuel continues to flow through said slow idle systemthroughout the operating range of the engine. The fuel flows involvedare so small however, since the port area 166 is adjusted to meet slowidle requirements, that the slow idle system has very little enricheningeffect on the fuel air ratio beyond the idle range. For fuel flows inthe idle range but beyond slow idle it is preferable that the adjustmentof spring 100 is such that the fuel flow from nozzle 72 plus that frompassageway 158 satisfy the-engine requirements in this range. Thisadjustment is easily made at 101, which functions as a vernier to meetexact flow requirements, the basic idle'flows being established by valve80.

When throttle valve 22 is substantially closed, as at slow idle,throttle lever 86 holds control rod 84 in its maximum rightward positionso that valve establishes a minimum flow area at port 74. The onlyreason for valve 80 being open at all at slow idle is to prevent anabrupt change in fuel flow when the transition to fast idle occurs. Theair metering force acting on diaphragm 30 is insuflicient to openregulator valve 50, but spring 58 opens valve 50 a degree which allowsan unmetered fuel pressure buildup in chamber 28 sufficient to balancethe spring force. Spring of discharge nozzle valve 92 may be adjusted toestablish the desired metered fuel pressure in conduit 76. Inthis'manner accurate control of the pressure differential acrossvariable metering area 74 is established throughout most of the idlerange.

As throttle lever 86 is rotated clockwise, thereby opening throttlevalve 22, the pressure differential across diaphragm 82 moves valve 80out of port 74 allowing the fuel flowto increase at a predeterminedrate. When valve 80 no longer acts to restrict port 74 the engine isoperating in the cruise range and metering jet 68, being smaller in areathan port 74, takes over the metering function.

Figure 2 shows a modification of the slow idle device shown in Figure 1.Similar parts have been similarly numbered. A portion of the airinduction passage on the manifold side of the throttle valve is shown at12. The discharge nozzle is shown generally at 72, impact air being bledthereinto from conduits 38, 79, and 81. The main metering jet is shownat 68. Conduit 70 contains fuel at unmetered pressure when thecarburetor is operating in the idle range and at metered pressure beyondthe idle range. Chamber 161 f the slow idle system communicates withconduit 79 through conduit 176. The desired slow idlefuel flowisestablished by adjustment of valve 168. At fuel flows beyond the idlerange it is apparent that the slow idle system flows a steadilydecreasing amount of fuel as the air flow increases since, in thisrange, the metered fuel pressure is steadily decreasing due to theincreasing vacuum in chamber 94 as previously explained. This effectreduces the fuel flow through the slow idle circuit to an absoluteminimum at air flows beyond the idle range.

Figure 3 shows another modification of the slow idle system. Similarparts have been numbered as in Figure l. The description of Figure 2pertains here excepting the venting ofchamber 161. Herein, chamber 161is vented .to chamber 96 of discharge nozzle valve 92 through. conduit178. Charnber 96 is at metered fuel pressure throughout the range ofoperation of the carburetor. Since metered fuel pressure decreases at arate proportional to the increase in mass air flow as heretofore,explained, the fuel pressure differential across slow idle jet 166likewise decreases for any given impact air pressure and slow idle fuelflow therefore varies inversely as a function of air flow throughout therange of carburetor operation.

Figures 4 and 5 show the slow idle system of Figures 1, 2 and 3 incombination With an engine primer attachment in which a lever 180 issuitably attached to the slow idle adjustment valve 168, as at 182, atthe one end thereof, and is manually controllable by a Bowden wire 184at the opposite end thereof. Resilient means 186 holds lever 180 againsta stop 188 at all times except when manual control 184 is actuated to anoperative position. Chamber 161 may be vented to either of chambers 2.8,70 or 96, as desired, through conduit 190. Arcuate slots 192 and 192' inlever 180 are provided so as to allow adjustment of valve 168.

In operation, actuation of lever 180 turns valve 168 out of jet 166,thereby increasing the flow of fuel through jet 166 and the mixtureratio to the engine. When control 184 is released, resilient means 186returns lever 180 to the stop abutting position shown in Figure 5, inwhich position valve 168 is adjusted so that jet 166 flows the desiredslow idle fuel. An automatic control means, such as a temperaturecontrolled actuator, may be substituted for the manual control shown at184.

Although several modifications of the invention have been particularlydescribed, it is understood that many changes might be made inthe formand arrangement of the parts without departing from the scope of theinvention.

I claim:

1. In a fuel metering device, an air induction passage, a venturi insaid passage, a throttle in said passage downstream of said venturi, amain fuel conduit adapted to supply fuel from a source undersuper-atmospheric pressure to said passage, a metering jet in saidconduit, a valve in said conduit upstream of said jet, a first meansresponsive to air flow through said passage for controlling said valve,a valve in said conduit downstream of said jet, a second meansresponsive to air flow through said passage for controlling said secondmentioned valve, a passageway connecting said conduit upstream of saidjet with said induction passage on the engine side of said throttle, ametering jet in said passageway, a chamber in said passageway adjacentthe discharge end thereof, and a conduit connecting said chamber to asource of air at substantially atmospheric pressure.

2. In a fuel metering device, an air induction passage, a venturi insaid passage, a throttle in said passage downstream of said venturi, amain fuel conduit adapted to supply fuel from a source undersuper-atmospheric pressure to said passage, a metering jet in saidconduit, a valve in said conduit upstream of said jet, a first meansresponsive to air flow through said passage for controlling said valve,a valve in said conduit downstream of said jet, a second meansresponsive to air flow through said passage for controlling said secondmentioned valve, and a passageway connecting said conduit upstream ofsaid jet with said induction passage on the engine side of saidthrottle.

3. In a fuel metering device, an air induction passage, a venturi insaid passage, a throttle in said passage downstream of said venturi, amain fuel conduit adapted to supply fuel from a source undersuper-atmospheric pressure to said passage, a metering jet in saidconduit, a valve in said conduit upstream of said jet, a first meansresponsive to air flow through said passage for controlling'said valve,a valve in said conduit downstream of said jet, a means for controllingsaid second mentioned valve, a passageway connecting said conduitupstream of said jet with said induction passage on the engine side ofsaid throttle, a metering jet in said passageway, a chamber in saidpassageway adjacent the discharge end thereof, and

a conduit connecting said chamber to a source of air at substantiallyatmospheric pressure.

References Cited in the file of this patent UNITED STATES PATENTS

